A simple dynamic model describing the age development of juvenile criminal behavior is extracted from such criminological theories as career theory, learning theory, and rational choice theory. The resulting nonlinear model appears to be as good as, or in some aspect better than, a static correlational model in explaining data from the longitudinal Utrecht Study of Adolescent Development. The model provides the basis for a more systematic study of nonlinear dynamic models for the description of the development of learning of criminal juveniles.